Kinesiological research has identified a number of factors that need to be present to provide optimal exercise. Optimal exercise will produce the best physical results the fastest and subsequently require a minimal amount of time to maintain fitness--all important considerations from a user's point of view. The following are the salient factors in optimal muscle exercise:
(1) Dynamically varied resistance--A muscle should be stressed near its maximum throughout its full excursion. Since muscles exert forces on the external world through the skeletal system, and since the mechanical advantage of the muscle/skeletal system is constantly varying as it moves; the external load (resistance) must vary with this motion to stress the muscle fully at each position.
(2) Full Muscle Excursion--It has been determined that full muscle excursion under stress is vitally important to its fitness and development. Stressing a muscle isometrically (i.e. at one position) simply does not produce full muscle fitness. Additionally, considerations of body flexibility and the desire to minimize the potential for muscle rupture dictate full muscle excursion.
(3) Specificity--Exercise routines, and devices involved in them, should address muscles as specifically as possible. This specificity permits the full stressing (1st axiom) of the intended muscle without over or under stressing adjacent or associated muscles. It also permits a focusing or tailoring of the exercise program to meet individual goals.
(4) Rotational Resistance--The human body is a collection of hinged links. Muscles drive these linkages about natural pivots (e.g. elbows, knees), sometimes about a multiplicity of axes (e.g. shoulders). In order to achieve "specificity" it is advantageous to exercise the muscles associated with each hinge point in rotation about that hinge point.
(5) Positive and Negative Work --Both positive (contracting) and negative (extending) muscle work are necessary for optimal muscle development and fitness. Exercise systems which do not load muscles that are extending (e.g. frictional systems) are missing an important half of the exercise cycle.
(6) Pacing--The rate at which an exercise is performed is important depending on the end result that is desired. For cardio-vascular stimulation and fitness exercise, pace should be based on the user's pulse rate.
(7) Individual Routines--Humans differ and the correct exercise routines likewise vary depending upon sex, age, size, condition, and desired results or goals of the fitness program.
The exerciser of the invention, as will become evident as the description proceeds, has been devised particularly to meet all of the criteria set forth above.
Equally important as a properly designed exercise from a physiological point of view is the psychological motivation provided to the user by the exercise routine or system. In the exerciser to be described, the motivational aspects may be provided through electronic/video games and challenges; video/audio instructions, rewards, and encouragements; and personalized electronic bookkeeping of progress toward goals and fitness as measured against past performance levels.
As mentioned above, the exerciser of the invention uses symmetrical muscle groups, working in opposition to one another, to produce safe, effective exercises without working against external weights or other forms of externally imposed resistances. The principle upon which the exerciser of the invention are predicated may be understood by considering a weightlifter. When a weightlifter lifts a single weight with both arms, his two arms do positive, that is contractile, muscle work. Now, when he lowers the weight, in a controlled manner, his two arms do negative, that is extensive, muscle work of an equal but opposite amount. When doing the positive muscle work, the weightlifter puts energy into the weight in the form of potential energy. Then, when doing the negative work, the muscles of the weightlifter absorb energy from the weight equal to the potential energy.
By separating the weight into two equal weights, the same exercise may be performed in the same manner by the weightlifter holding one weight in each arm, and by moving both arms up and down in unison. Moreover, the exercise now can also be performed by raising one arm while the other arm is being lowered, and vice versa. Over one full cycle the amount of positive and negative work performed in both cases is the same.
The exerciser of the present invention is constructed such that the two limbs are moved in a manner described immediately above, with one doing positive muscle work while the other does negative muscle work.